Generally air conditioners and air conditioning-related devices of homes, buildings, and the like in North America conventionally use a thermostat, that is, an air conditioning control device. The expression “air conditioning-related devices”, for example, includes devices such as auxiliary heat sources and fans. The thermostat has a temperature setting function, performs ON/OFF control of power supply to the air conditioner or air conditioning-related device in accordance with a set temperature and a temperature measured by the thermostat (temperature measurer), and controls operation of the air conditioner or air conditioning-related device. In recent years thermostats are marketed that display information such as an operating time and air conditioner power consumption, or that store the daily operating times of the air conditioner and automatically set an operating schedule of the air conditioner in accordance with the stored daily operating times. Further, standardization of the wiring format of thermostats guarantees interchangeability among the thermostats of different manufacturers.
Further, air conditioners marketed in recent years include an inverter circuit, and such air conditioners can use the inverter circuit to adjust rotation speed of a compressor in response to a temperature difference between indoor temperature and the set temperature. By use of the air conditioner that includes the inverter circuit, the rotation speed of the compressor can be appropriately adjusted in response to the temperature difference between the indoor temperature and the set temperature. Specifically, when using this type of air conditioner, the rotation speed of the compressor is decreased as the temperature difference between the indoor temperature and the set temperature decreases. Such operation can decrease fluctuation range of the indoor temperature. Further, rotation speed of the compressor can be maintained at a required minimum limit by raising and lowering the rotation speed of the compressor in response to the temperature difference between the indoor temperature and the set temperature, and thus such operation can lower power consumption by the air conditioner accordingly.
The thermostat, in the aforementioned manner, transmits to the air conditioner only information indicating whether to turn ON or OFF the power supply. Thus when using the air conditioner that includes the inverter circuit, control by appropriate adjustment of rotation speed of the compressor in reaction to the temperature difference between the indoor temperature and the set temperature is not possible, and the power consumption by the air conditioner and fluctuation rate of the indoor temperature are not sufficiently reduced.
In contrast, a mediating device is proposed, as in Patent Literature 1, that mediates between the thermostat and the air conditioner that includes the inverter. This mediating device, upon detection of a change of output of the thermostat, determines the set temperature of the air conditioner on the basis of an intake temperature measured by the air conditioner. Specifically, the mediating device calculates an mean value of the intake temperature obtained when the output of the thermostat changes from ON to OFF and the intake temperature obtained when the output of the thermostat changes from OFF to ON, and the mediating device uses the calculated mean value as an air conditioning target temperature value. Then the mediating device transmits the calculated air conditioning target temperature value to the air conditioner. The air conditioner adjusts rotation speed of the compressor in a step-wise manner such that the intake temperature measured by an intake temperature sensor becomes the air conditioning target temperature value received from the mediating device.